3.2.3. Hydroformylation 2467 3.2.4. Dimerization 2468 3.2.5. Oxidative Cleavage and Ozonolysis 2469 3.2.6. Metathesis 2470 4. Terpenes 2472 4.1. Pinene 2472 4.1.1. Isomerization: R-Pinene 2472 4.1.2. Epoxidation of R-Pinene 2475 4.1.3. Isomerization of R-Pinene Oxide 2477 4.1.4. Hydration of R-Pinene: R-Terpineol 2478 4.1.5. Dehydroisomerization 2479 4.2. Limonene 2480 4.2.1. Isomerization 2480 4.2.2. Epoxidation: Limonene Oxide 2480 4.2.3. Isomerization of Limonene Oxide 2481 4.2.4. Dehydroisomerization of Limonene and Terpenes To Produce Cymene 2481

Chemical Routes for the Transformation of Biomass into Chemicals

基礎講座 電気泳動(Electrophoresis)

 Many atmospheric chemicals occur in the gas phase as well as in liquid cloud droplets and aerosol particles Therefore, it is necessary to understand the distribution between the phases According to Henry's law, the equilibrium ratio between the abundances in the gas phase and in the aqueous phase is constant for a dilute solution Henry's law constants of trace gases of potential importance in environmental chemistry have been collected and converted into a uniform format The compilation contains 17 350 values of Henry's law constants for 4632 species, collected from 689 references It is also available at http://wwwhenrys-laworg 

/pdf/compilation-of-henry-s-law-constants-version-4-0-for-water-58il9q0ogv.pdf

Compilation of Henry's law constants (version 4.0) for water as solvent

Identification of volatile components in basil Ocimum basilicum L and thyme leaves Thymus vulgaris L and their antioxidant properties

There is a continuing need for the development of effective, cheap and environmentally friendly processes for the disinfection and degradation of organic pollutants from water. Ozonation processes are now replacing conventional chlorination processes because ozone is a stronger oxidizing agent and a more effective disinfectant without any side effects. However, the fact that the cost of ozonation processes is higher than chlorination processes is their main disadvantage. In this paper recent developments targeted to make ozonation processes cheaper by improving the efficiency of ozone generation, for example, by incorporation of catalytic packing in the ozone generator, better dispersion of ozone in water and faster conversion of dissolved ozone to free radicals are described. The synthesis of ozone in electrical discharges is discussed. Furthermore, the generation and plasma chemical reactions of several chemically active species, such as H2O2, O•, OH•, HO2•, O3*, N2*, e-, O2-, O-, O2+, etc, which are produced in the electrical discharges are described. Most of these species are stronger oxidizers than ozone. Therefore, water treatment by direct electrical discharges may provide a means to utilize these species in addition to ozone. Much research and development activity has been devoted to achieve these targets in the recent past. An overview of these techniques and important developments that have taken place in this area are discussed. In particular, pulsed corona discharge, dielectric barrier discharge and contact glow discharge electrolysis techniques are being studied for the purpose of cleaning water. The units based on electrical discharges in water or close to the water level are being tested at industrial-scale water treatment plants.}

https://iopscience.iop.org/article/10.1088/0963-0252/10/1/311/pdf

Water purification by electrical discharges

Preface. Preface to the First Edition. List of Acronyms and Symbols. 1. General introduction. 1.1 Principles of headspace analysis . 1.2 Types of headspace analysis. 1.2.1 Principles of static headspace - gas chromatography (HS-GC). 1.2.2 Principles of dynamic headspace -- gas chromatography. 1.3 The evolution of the HS-GC methods. 1.4 Headspace -- gas chromatography literature. 1.5 Regulatory methods utilizing (static) HS-GC. 1.6 References. 2. Theoretical background of HS-GC and its applications. 2.1 Basic theory of headspace analysis. 2.2 Basic physicochemical relationships. 2.3 Headspace sensitivity. 2.3.1 Influence of temperature on vapor pressure and partition coefficient. 2.3.2 Influence of temperature on headspace sensitivity for compounds with differing partition coefficients. 2.3.3 Influence of sample volume on headspace sensitivity for compounds with differing partition coefficients. 2.3.4 Changing the sample matrix by varying the activity coefficient. 2.4 Headspace linearity. 2.5 Duplicate analyses. 2.6 Multiple headspace extraction (MHE). 2.6.1 Principles of MHE. 2.6.2 Theoretical background of MHE. 2.6.3 Simplified MHE calculation. 2.7 References. 3. The technique of HS-GC. 3.1 Sample vials. 3.1.1 Types. 3.1.2 Selection of vial volume. 3.1.3 Vial cleaning. 3.1.4 Wall adsorption effects. 3.2 Caps. 3.2.1 Pressure on caps. 3.2.2 Safety closures. 3.3 Septa. 3.3.1 Types. 3.3.2 Septum blank. 3.3.3 Should a septum be pierced twice?. 3.4 Thermostatting. 3.4.1 Influence of temperature. 3.4.2 Working modes. 3.5 The fundamentals of headspace sampling systems. 3.5.1 Systems using gas syringes. 3.5.2 Solid-phase microextraction (SPME). 3.5.2.1 Comparison of the sensitivities in HS-SPME and direct static HS-GC. 3.5.3 Balanced-pressure sampling systems. 3.5.4 Pressure/loop systems. 3.5.5 Conditions for pressurization systems. 3.5.6 The volume of the headspace sample. 3.5.6.1 Sample volume with gas syringes. 3.5.6.2 Sample volume with loop systems. 3.5.6.3 Sample volume with the balanced-pressure system. 3.6 Use of open-tubular (capillary) columns. 3.6.1 Properties of open-tubular columns for gas samples. 3.6.2 Headspace sampling with split or spitless?. 3.6.3 Comparison of split- and splitless headspace sampling. 3.6.4 Band broadening during sample introduction. 3.6.5 Temperature influence on band broadening. 3.6.6 The combination of different columns and detectors. 3.7 Enrichment techniques in HS-GC. 3.7.1 Systems for cryogenic trapping. 3.7.1.1 Systems for Cryogenic condensation. 3.7.1.2 Trapping by cryogenic focusing. 3.7.1.3 Influence of temperature on cryogenic focusing. 3.7.1.4 Comparison of the various techniques of cryogenic trapping. 3.7.2 Influence of water in cryogenic HS-GC. 3.7.2.1 Water removal in static HS-GC. 3.7.2.2 Applications. 3.7.3 Enrichment by adsorption. 3.7.3.1 Water removal from an adsorption trap. 3.8 Special techniques with the balanced-pressure systems. 3.8.1 Instrumentation for MHE. 3.8.2 Backflushing. 3.9. Reaction HS-GC. 3.9.1 Derivatization in the headspace vial. 3.9.1.1 Methylation. 3.9.1.2 Esterification. 3.9.1.3 Transesterification. 3.9.1.4 Acetylation. 3.9.1.5 Carbonyl compounds. 3.9.2 Subtraction HS-GC. 3.9.3 Special reactions. 3.9.4 HS-GC analysis of volatile derivatives from inorganic compounds. 3.10 References. 4. Sample handling in HS-GC. 4.1 Equilibration. 4.1.1 Gas samples. 4.1.2 Liquid samples. 4.1.3 Solid samples. 4.2 Solution approach. 4.3 Sample handling and sample introduction. 4.3.1 Gas samples. 4.3.2 Liquid samples. 4.3.3 Solid samples. 4.4 Preparation of standard solutions. 4.4.1 Preparation of a standard solution from a liquid or solid substance. 4.4.2 Preparation of a standard solution from a gaseous compound. 4.5 Influence of the matrix. 4.5.1 Clean matrix is available. 4.5.2 Matric effect can be eliminated. 4.5.3 Artificial matrix can be prepared. 4.6 Methods aiming the complete evaporation of the analyte. 4.6.1 The total vaporization technique (TVT). 4.6.2 The full evaporation technique (FET). 4.6.3 Calculation of the extraction yield in FET. 4.6.4 Comparison of headspace sensitivities. 4.7 References. 5. Headspace methods for quantitative analysis. 5.1 Internal normalization. 5.2 Internal standard method. 5.3 External standard method. 5.4 Standard addition method. 5.4.1 Single addition. 5.4.2 Handling of the added standard (Gas-phase addition and sample-phase addition). 5.4.3 Determination by multiple additions. 5.5 Multiple headspace extraction (MHE). 5.5.1 Principles of MHE. 5.5.2 Calibration in MHE. 5.5.2.1 External standard. 5.5.2.2 Internal standard. 5.5.2.3 Standard addition. 5.5.3 The use of gaseous external standards in MHE. 5.5.4 The role of quotient Q. 5.5.4.1 Relationship between Q and pressures. 5.5.4.2 Value of Q in the case of total vaporization. 5.5.4.3 The relative position of the MHE plots as a function of Q. 5.5.5 The correlation coefficient (r). 5.5.6 Evaluation of the shape of the regression plot. 5.5.7 Influence of K/s. 5.6 Analysis of solid samples (adsorption systems). 5.6.1 Suspension approach. 5.6.2 Surface-modification techniques. 5.6.3 Highly adsorptive samples. 5.7 Calibration techniques with headspace samples of varying volumes. 5.8 Analysis of gas samples. 5.9 References. 6. Method development in HS-GC. 6.1 General guidelines. 6.2 Determination of the residual monomer content of polystyrene pellets. 6.2.1 First approach: use of internal standard with MHE. 6.2.2 Second approach: single determination with internal standard. 6.2.3 Third approach: use of external standard with MHE. 6.2.4 Fourth approach: use of the solution approach. 6.3 Determination of residual solvents in a printed plastic film. 6.3.1 First approach: use of external standard with MHE. 6.3.2 Second approach: use of standard addition with MHE. 6.3.3 Third approach: use of internal standard. 6.4 Determination of the volatile constituents of a cathodic electrolytic plating bath. 6.4.1 First approach: use of external standard with MHE. 6.4.2 Second approach: dilution and use of external standard. 7. Nonequilibrium static headspace analysis. 7.1 Accelerated analysis. 7.2 Heat-sensitive samples. 7.3 References. 8. Qualitative analysis by HS-GC. 8.1 The use of HS-GC in 'fingerprinting.'. 8.2 The use of headspace sampling in hyphenated systems. 8.3 The use of HS-GC in microbiology. 8.4 References. 9. Special measurements. 9.1 Determination of vapor pressures. 9.2 Determination of activity coefficients. 9.3 Determination of related physicochemical functions. 9.4 Determination of phase distribution (partition coefficient). 9.4.1 The vapor-phase calibration (VPC) method. 9.4.2 The phase-ratio variation (PRV) method. 9.4.3 MHE methods for the determination of the partition coefficient. 9.5 Reaction constant measurements. 9.6 Determination of solute solubility by MHE. 9.7 Gas-solid systems. 9.7.1 Determination of adsorption isotherms. 9.7.2 Determination of the rate of release of a volatile analyte. 9.8 Validation of the headspace instrumentation: investigation of detector linearity and detection limit. 9.8.1 Definitions. 9.8.2 Linear range of the detector. 9.8.3 Precision of the range. 9.8.4 Minimum detectability. 9.9 References. Index.

Static Headspace-Gas Chromatography: Theory and Practice

Encyclopedia of Industrial Chemical Analysis

The new phase ratio variation method is described which represents a convenient way for the determination of gas-liquid partition coefficients for practical purposes, utilizing equilibrium headspace-gas chromatography (EHS-GC). This method is based on the relationship between reciprocal peak area and the phase ratio in the vial containing the sample solution; it involves regression analysis of the EHS-GC measurements of a number of sample vials containing the same sample solution but with a wide variation of phase ratios. Examples are given for both aqueous systems and systems consisting of a stationary (liquid) phase used as the solvent; comparison of the measured values with results obtained by other methods shows satisfactory agreement. A critical discussion of the conditions influencing the accuracy of the analytical results is given.

Determination of gas-liquid partition coefficients by automatic equilibrium headspace-gas chromatography utilizing the phase ratio variation method

Open Tubular Columns in Gas Chromatography

Multiple headspace extraction (MHE) is an absolute quantitative method used in static headspace—GC. In principle it is dynamic gas extraction, carried out stepwise and establishing equilibrium conditions in each step. The concentration of the analyte in the headspace decreases exponentially during the series of extraction steps: by proper mathematical extrapolation the total peak area proportional to the total amount of analyte present in the original sample can be obtained. This paper investigates MHE from the theoretical point of view using two approaches: a simplified theory regarding MHE as a first-order reaction, and a rigorous, step-by-step treatment of the MHE procedure. Special consideration is given to the fact that the headspace gas is only partially removed between individual steps. As shown, the results of both treatments are essentially the same hence the method is theoretically sound. The practical limitations of MHE are also discussed pointing out how the analytical parameters may be adjusted to improve the possibility of determination by MHE.

Leslie S. Ettre

Papers

Static Headspace-Gas Chromatography: Theory and Practice

Encyclopedia of Industrial Chemical Analysis

Determination of gas-liquid partition coefficients by automatic equilibrium headspace-gas chromatography utilizing the phase ratio variation method

Open Tubular Columns in Gas Chromatography

Theory and practice of multiple headspace extraction